Air pump



D. G. EDWARDS.v

AIR PUMP.

APPLicATloN FILED 1ML I9, :920.

Patented Feb. 7, l1922.

UNITED lSTATES DANIEL GORDON EDWARDS, OF HOPKINSYILLE, KENTUCKY. v

Am PUMP..

'Specification of Letters Patent. Patented Feb. 7, 1922.

Application filed January 19, 1920. Serial No. 352,297.

To all whom t may concern.'

Be it known that I, DANIEL GORDON EDWARDS, a citizen of the United States, residing at Hopkinsville, in the county of Christian and State of Kentucky, have inv4 vented certain new and useful Improvements in Air Pumps, of which the following is a specification.

This invention relates to air pumps, and more articularly to pumps employed for the in ation of pneumatic tires, and the like.

Vhile especially useful in connection with manually operated air compressors of the type commonly known as foot pumps, which type I have shown in the drawings, by way of illustration, it will be understood that my improvements are not limited to such use, as the invention, in its broader aspects, is equally applicable to other types vof pumps, either compression or vacuum.

Inreciprocating air pumps as ordinarily constructed, the piston comprises a flexible, cup shaped member, usually of leather, intended to make a substantially air-tight fit within the barrel or cylinder, fiuid pressure being relied upon to force the edges of such cup leather against the walls of the cylinder to prevent leakage past the same. It has been found in practice, however, that the leather cu through lack of proper lubrication and ot er causes, frequently becomes stiff and more or less rigid, and this, together with reduction in the-diameter of the cupdue to wearer shrinkage, results in the free escape of air past the piston, and makes it impossible to produce a high compression or vacuum. p

It has heretofore been proposed to press the edges of the leather cup into contact with the vcylinder walls by means of an expander block or the like urged by a. spring, but in such an arrangement the spring pressure is constant, being effective during the idle stroke as well as the working stroke, and this continual pressure serves to wear away the leather very rapidly.

It is the primary object of the present invention to provide positive mechanical means for expanding the cup leather into close contact with the cylinder walls during the working stroke, and to permit the same to retract during the idle stroke, whereby high compression is secured, and wear reduced to a minimum. In carrying out this object, I propose a construction in which the expanding force increases in directproportion to the load or resistance encountered b y the piston, so that the higher the compression the tighter the fit of the cup leather within the barrel. anyl and all loads is effectively prevented.l

A further vobject is to combine the expander feature above described, with. a ositive, mechanically actuated valve for a mitting air into the cylinder through the piston, during its idle or return stroke.

With the above objects in view, and to improve generally on the structural details of such apparatus with a view to increasing its efficiency, the -invention consists in the construction, combination and arrangement of' arts hereinafter described and claimed, an illustrated in the accompanying drawing, in Which:-

Fig. l is a longitudinal section through a foot pump embodying my improvements;

Fig. 2 is an end elevation of the operating handle, the piston rod being in section;

Fig. 3 is an end view o-f a cup shaped spring which I employ;

Fig..4 is a side view thereof;

Fig. 5 is a side view of a resilient metallic cup, which I employ inside of the usual flexible cup; l

Figs. 6 and 7 are fragmentary longitudinal sections similar to Fig. 1, but showing modified constructions, and

Fig. 8 is a sectional view of the operating handle similar to Fig. l, but showing a sli htly modified arrangement.

eferring to the drawings in detail, and more particularly to Figs. l and 2 thereof, my improved ump comprises the usual cyl- In this way, leakage atinder or barre l, which in practice is'preferably formed of brass tubing. This barrel is screwed into a base or pedestal 2, carrying the usual loop or stirrup 3, into which the operators foot is inserted. In order to prevent the pump from slipping, I prefer ably provide one or more spurs 4 on theunder side of the stirrup, such spurs serving to engage the surface on whichthe stirrup rests.

In the base 2 is formed a recess 5 for a purpose hereinafter described and from this recess extends the delivery port with which the usual elbow 6, preferably carrying a check valve, connects. For the purpose of tire inflation, a flexible hose 8 is attached to the elbow 6, by meansV of a coupling 7, the end of the coupling inserted inthe hose preferably being threadedas indicated at `7, and the hose, l adjacent such threaded portion,. being surroundedby av suitable` clamp Working within the cylinder or barrel 1 is a piston carried by a piston rod 10, which rod consists of a small piece of pipe or tubing, as shown.- The end4 of the barrel opposite to the base is closed b a cap or cover 11 preferably having air oles 12 therethrough.

The 'piston comprises a rigid plate or disc 13 screw threaded onto the iston rod 10 and a superposed disc 14 of sof absorbent material, such as felt. A washer 15 secures the felt disc in position. This felt disc is for the purpose of absorbing asuitable lubricant, and thus keeping the piston in working order.

Adjacent the ri id disc 13 is the usual flexible cup 17 pre erably formed of leather or the like, and inside of this iiexible cup is a metallic cup 18 having resilient side walls, preferably slit ,as shown in Fig. 5 to permit expansion. 'It will be noted that the flexible cup \17 is held between the resilient cup 18 and the disc 13 'and that such rigid disc is mounted between the iexible cup and absorbent washer 14.

Secured to the extreme end of the piston rod 10 inside of the resilient cu 18 is a valve sea-t 27, preferably forme of rubber or the like, and co-'operating with this valve seat, is a valve 28.

Fitting within the resilient cup 18 and reversely disposed in respect thereto is a cup shaped spring 19, clearly shown in Figs. 3 and 4. This comprises a marginal portion provided with slits 19, which slits extend radially inward towards the center and with a raised central portion 19b having an opening therethrough.,4 This opening fits over the endl of a pull rod 21, which extends down through the hollow piston rod 10, and the-spring member 19 is secured on the screw-threaded end of such rod, by means of lock nuts 20. The valve 28 is mounted on the rod 21 within the hollow of the cup shaped spring 19, and is also provided With a lock nut. It will be understood that the position of the parts 19 and 28 relative to each other and to the `metallic cup and valve seat can be adjusted as Rigidlysecured to the outer end of piston rod 10 is atrans-versely extending operating handle 22, held in position by means of a nut 23. A spring 10n is interposed be- Vtween this handle and the cap 11'to cushion the movement of the piston, and prevent hammering thereof against the base 2.

' Pivoted to the handle y22 as' at 26 is a lever 25shown in F ig. 1 as being' similar to the handle 22. Instead of this construction, however, the operating handle may be symmetrical with respect to the rod 10, as

indicated at 32in Fig. 8, and an operating lever such as 35 may be pivoted at 36 to suchhandle, a spring 33 being in this case preferably interposed between the handle and lever and tending to move the lever in one direction.

` The outer endof the pull rod orv valve rod 21 is pivotally connected at 24 to the handle lever 25 shown in Fig. 1, or to the lever 35 shown in Fig. 8, as the' case may' be. Whichever construction is employed, it will be apparent that when the handle is grasped by the operator, and pressure applied in such a direction as to produce a Working stroke of the piston, the lever 25 or 35 will first be given an initial pivotal movement, relative to the handle, and this,

initial pivotal movement'exerts a pull upon the rod 21. This pull simultaneously produces two results, lirst, it closes the valve 28 against its seat 27, and, second, it exerts pressure against the convex middle portion of the cup shaped springs 19, thus causing such spring to expand radially, thereby expanding the cups 17 and 18 and forcing the former into intimate contact with the walls Vof the cylinder. The continued application of force to the operating handle in the same direction produces the working stroke ofthe piston, thus driving out the air contalned between itself and the base 2. The recess 5 in the base 2 is adapted to receive the lock nuts 20 and convex portion 19b of the cup shaped springs 19, thus permitting the working portion of the piston to approach the base-2 very closely. This reduces the necessary clearance to a minimum and enables the pump to work ver eiiciently.

On the return or idle stro e of the piston, the'lever 25 partakes of an initial pivotal movement in the other direction, thus opening the valve 28 and relieving the pressure on the cup shaped spring 19. This permits the resilient and flexible cups to contract and through the valve 28 into the barrel of the.

pump. It will be noted that the outer end of the hollow piston vrod 10 is also open, so that air mayrenter through this channel as well. y

vInstead of employing the cup shaped spring shown in Fig.' 1, I may use a solid or non-resilient spreader as shbwn in Fig. 6. Referring to this figure, it will be seen that I mount a conical or tapered block or plug 29 on the end of the pull rod 21,

, a tapering surface of this block engaging the edges of the resilient cup 18, and this expands the same as the flexible cup 17. In this connection it may be stated that the purpose of the resilient cup 18 in both of these modifications `is to hold the flexible cup and prevent it from wrinkling or buckling, as might be the case if the spreader directly engaged such flexible cup.

In Fig. 7 I have shown still further modification in which, instead of the taperin block 29, I employ a flat rigid disk 39 pre*- erably having openings therethrough. Thls disc, itself, serves as a valve to engage the valve'seat 37 and its outer edges are preferably rounded or bevelled. These .rounded edges engage a conical portion 38a of a special form of resilient cup 38, and thus expands such cup as the disc 39 is moved axially into valve closing position. In thls case a reinforcing washer 30 is used to sup- 'port the flexible cup 17 which is necessarily .ther discussion.

What I claim is:

l. .In an air pump, the combination with a cylinder and piston, of positively acting mec anical means for causing the piston to expand so as to lit the cylinder tightly during the working stroke, and permitting 1t to contract: so as to slide freely therein during the idle or return-stroke.

2. In an air pump, the combination with a cylinder, and a piston working in the same, and comprising a flexible cup, of mechanical means for expanding the. sides of said cup into contact with the cylinder walls with a force always proportional to the load or resistance against which the piston is working.

3. In an air pump, the combination with a cylinder, and a piston working in the same, and comprising a flexible cup, .of mechanical means for expanding the sidesof said cup into Contact with the cylinder walls during the working stroke and permitting the retraction of said cup during the idle or return stroke.

4. In an air pump, the combination with a cylinder and piston, said piston/comprising 'a exible cup, of a hollow piston.i rod to which said plston is secured, and means extending through said hollow rod for expanding said cup into close contact with the cylinder walls during the working stroke of the piston, and permitting the retraction of said cup during the return stroke.

5. In an air pump, the combination with a cylinder and piston, said piston comprising .a flexible cup, ofa hollow piston rod to which said piston is secured, a handle secured to the outer end of said rod, a lever pivoted to said handle, and means extending throu h said rod and connected with said lever or expanding said cup into close contact with the cylinder walls.

. 6. In an air pump, the combinationwith a cylinder and piston, said piston comprising a flexible cup, a piston rod, a transversely disposed handle rigidly secured to said rod,

a lever pivoted to saidy handle, and meansA operated by said lever during the working stroke of t e pump for expandlng the. said cup into close contact with the cylmder walls.

7. In an air pump, the combination with a cylinder and piston, said piston comprising a flexible cup, a piston rod, a lever extending transversely of said rod and adapted to be grasped by the hand when the pump is operated, and means actuated by said lever for expanding the said cup into .close contact with the cylinder walls when force is applied to said lever in a direction to produce a working stroke of the piston.

8. In an air pump, the combination with a cylinder and piston, said piston comprising a flexiblev cup, a piston rod, an operatin handle extending transversely of the said rod and comprismg a portion capable of an initial movement independent of said rod, and means actuatedby such initial movement of said portion for expanding said cup into contact with the walls of the cylinder.

9. In anair pump, the combination with a cylinder, and piston, said piston comprising a'flexible cup, of a piston rod, a valve in said plston, a transverse handle secured to said rod, a lever pivoted to said handle, andl means actuated by said lever for expanding said cup and simultaneously closing said Valve.

10. In an air pump, the combination with a cylinder and piston, said piston comprising a iexible cup, of a valve in said iston, and mechanical means for positive y expanding said cup and simultaneously closing said valve during the working stroke of the piston.

11. In an air pump, the combination with a cylinder and piston, said piston comprising a flexible cup, of a spreader located within said cup, and means for ap-plying force to said spreader axially of the pump cylinder during the working stroke only of the piston so as to cause it to expand said cup into close contact with the walls of the cylinder.r

12. In an air pump, the combination with a cylinder and piston, said piston comprising a flexible cup, of a spreader located within said cup, said spreader comprising a cup-shaped resilient member, and means for applylng pressure axially to the center of such member so as to cause it to expand lio a cylinder and piston, said piston comprising a flexible cup, of a resilient metallic cup fitting Within said flexible cup, and means operating inside of' said metalhc cup for expanding'both cups during the Working of the piston.

14. In an air pump, the combina-tion With a cylinder and piston', said piston comprising a flexible cup, of a resilient metallic cup fitting Within said flexible cup, a spreader operating inside of said metallic cup, and

means for applying force axially of the vcylinder to said spreaden to cause'it to expand both cups.

15. In an air pump, the combination with a cylinder and piston, said piston comprising a flexible cup, of a resilient metallic cup -iitting Within said flexible cup, a spreader located inside of said metallic cup and comprising a cup-shaped spring disposed reversely with respect to said metallic cup, means for compressing said spring axially so as to cause it to expandradially, and thus force the flexible cup into close contact with theJ cylinder Walls.

`16. In an air pump, the combination with a cylinder and piston, said piston comprising a resilient cup, of a hollow piston rod to which said piston is secured, a' valve seat formed at the end of said rod, a valve for said seat, a. valve rodextending through Said Ahollow piston rod, and movable axially it to contract so as to slide freely therein dur-in the return stroke.

18. n a pump, the combination with a cylinder and piston, of actuating means for the piston, and mechanical 'means for expandin the piston into close contact with the cy inder Walls during the working stroke, said expanding means comprising an element connected with the actuating means, and shiftable in a direction opposite to that of the piston travel by the in1t1al movement of said actuating means.

4In testimon whereof I allix my si ature.

DANI L GORDO-Ny EDWA DS. 

